Coded document reader



POWER SUPPLY AMPLIFIER nil.

mmvron JOHN H. HOWARD AGENT United States PatentO 1 Claim. (Cl. 250-78)This invention relates to an improved data handling system using spotsof fluorescent material for data recording and a combination of highenergy light irradiation and photosensitive scanning to read therecorded data, and is a division of applicants co-pending applicationentitled Coded Document Reader, Serial No. 577,143, filed April 9, 1956,now Patent No. 2,975,966.

Data handling poses a serious problem in many fields. It is acute in thebanking industry which faces a phenomenal increase in the volume ofactivity in the handling of checking and savings accounts. Currentlythere is excessive manual work involved in the processing of checks andsavings records. Automation would relieve this problem. The basicdetailed activities involving the receipt and the payment of funds arenot the point of critical concern. It is in the necessary maintenance ofthe records relating to deposit accounting that the serious problemarises. Some method and equipment is needed to provide a data link tocentralized accounting offices for this processing.

Another problem area has arisen in the field of ticketing for rail andair transportation. For each ticket sold there is a need to record theserial number of the ticket and the numerical code representing thenature of the trip sold. Central accounting needs this basic informationfor interline billing, revenue accounting, and for figuring the tax duein the various states or countries through which a trip passes.

Still another problem area is currently emerging in the handling of vastvolumes of information for organizations such as government departmentsand various military or naval staffs. In this area it is felt thatclassification and reduction of raw information preparatory to filing oranalysis could be greatly accelerated and improved in reliabilitythrough automation techniques.

Throughout many of the data handling problem areas for which automationappears desirable, there is an interest in preserving certain wellestablished forms, documents and other printed material which have awide acceptance and where the development of substitutes would be bothexpensive and of questionable advantage. The pass books, deposit ticketsand withdrawal orders in a savings bank operation are typical of suchitems. Accordingly it is considered advantageous to utilize fluorescentmaterials for practically invisible printing or coding on such documentswhich under ordinary light is invisible and does not interfere with theordinary matter printed thereon. This luminescent material could beirradiated with high energy invisible radiation such as actinic rays,ultraviolet light or soft X-rays, and the resulting luminescentradiation utilized in the data reading and recording operation.

Difliculties arise in the use of luminescent materials in that manysubstances have some degree of fluorescent quality. Bleaches that areused in paper, inks used in the normally legible printed matter thereon,smudges from greases and other foreign materials acquired duringprocessing and handling are typical of unwanted sources of luminescentsignals which will appear on such records which are exposed to highenergy radiation. These spurious signals add to the background noiselevel and reduce the signal-to-noise ratio of desired signals and mayeven present such a spurious level as to introduce a false signal. Thepresent invention is employed to read luminescent codings on records ina manner which enhances the signal-to-noise ratio. Throughout thedescription of this invention, the reading of coded data on a documentwill be referred to as scanning, inasmuch as the data is recorded in apattern of phosphorescent dots interspersed with areas or spots in whichno phosphorescent material has been deposited and these areas must beexamined or scanned. Scanning comprises the exposure of a photosensitivemeans to this recorded data pattern (when in an excited and radiatingstate) either in a predetermined sequence or with a matrix ofphotosensitive pickups wherein their positions correspond to particularparts of the data pattern.

An object of this invention is to provide an improved data handlingsystem.

Another object of this invention is to provide an improved readingdevice for data recorded by phosphorescent materials.

A further object is to provide an improved signal-tonoise ratio in aluminescent scanner, wherein high energy radiation and electrical fieldsincidental to the generation of this high energy radiation and spuriousshort-persistence fluorescence are eliminated from the background levelof the signal which is picked up.

In accordance with one feature of this invention, there is provided animproved photoelectric data irradiating and reading method andapparatus, having a radiation source for producing high energy photonsto irradiate the document carrying the data, recording the data inlong-persistence phosphorescent materials, exciting this phosphorescentmaterial with this radiation and removing the radiation a predeterminedtime interval before scanning, and scanning to read the phosphorescentlight which persists after short-persistent fluorescence from unwantedor spurious materials has subsided.

The foregoing and other objects of this invention Will be readilyunderstood from the following specification and claim together with theaccompanying drawing wherein:

FIG. 1a is a functional diagram of an electrically controlled systemconstructed in accordance with this invention;

FIG. 1b is a diagram of an amplifier useful in the system shown in FIG.Ia;

FIG. 1c is a plan view of a document and its coded data;

FIG. 2 is an intensity-vs.-time plot of fluorescent and phosphorescentresponse to radiant energy;

FIG. 3 is a functional diagram illustrating photographic scanning andrecording techniques as utilized in this invention;

FIG. 4a is a front view in diagrammatic form of an optical system whichmay be utilized in accordance with this invention;

FIG. 4b is a side elevation view of the optical system of FIG. 4a; and

FIGS. 5 and 6 are detailed sketches of devices featured in theinvention.

In the following description, phosphorescence is used for the signalluminescence having a long persistence after excitation by a radiantsource and fluorescence is used for the noise luminescence having littleor no persistence after the radiation expires. A typical phosphorescentmaterial comprises zinc sulphide and small percentages of added materialsuch as silver, with a persistence time in excess of many microseconds;and a typical fluorescent material is anthracene with a persistence timein the order of one microsecond or less.

Referring to FIG. 1a, an alternating voltage 20 is utilized forsynchronization of units as well as for supplying operating power. Anyconveniently useful voltage and frequency may be used, consistent withrequired irradiating and scanning periods and the frequency limitationsof various units. Power supply 21 provides alternate half cycles tooutput circuit 22 and the other alternate half cycles to output circuit23, so that the two sources of irradiation 24 and 25 are excitedtogether but alternately with amplifier 32 as to their respective on andoff periods. While square waves are shown as the input signals on leads22 and 23, other waveforms also are useful. Further, the duty cycle oneach pair of leads is less than 50%, or less than a half cycle so as toprovide a predetermined time interval between irradiation and scanningduring which the radiation from unwanted fluorescence and other noisessubsides before the desired radiation from long-persistencephosphorescent material is read.

The amplifier 32 may be of the type found in conventional dataprocessing systems. As shown diagrammatically in FIG. 1b, the inputleads are connected to contact of selector 19 and the amplifier inputcircuit is connected to these contacts in a predetermined sequence sothat the presence or absence of a signal, as determined by the presenceor absence of light on photocells of the scanning matrix 28, generates adigital signal which is amplified and applied to leads 33. When sources24 and 25 are on, amplifier 32 is off; and when sources 24 and 25 areoff, then the amplifier 32 is on and is responsive to signals fromphotocell assembly or matrix 28 which in turn has a plurality ofphotocells, each of which is sep arately responsive to incidentradiation from a particular area or cell on the surface of document 26,which is shown in perspective in FIG. 1a and in plan view in FIG. 1c andin accordance with the form of the invention claimed in a co-pendingdivisional application filed coincident with the present application.Data is represented in coded form on the document 26 by the presence orabsence of phosphorescent spots 27. Other unwanted sources offluorescence are shown as randomly placed areas 42.

Radiant sources 24 and 25 receive energy through leads 22, producinghigh intensity radiation capable of exciting phosphorescence in therecorded phosphor spots 27 of document 26. Radiations which have beenfound useful in producing fluorescence and phosphorescence areultraviolet light, actinic rays, and soft X-rays. In general, radiationsof wavelengths shorter than about 6,999 Angstrom units, or yellow light,are more useful because their energy per photon is higher. Sources 24and 25 therefore represent producers of such well known radiations.

Document 26, as shown in FIG. 1c, utilizes both visible printed matterand invisible data recorded as spots 27 of a phosphorescent material,such as zinc sulphide. Document 26 has spots 27 arranged in a codingpattern arranged in a predetermined number of possible cell areas suchas found in a matrix so as to present important information tosupplement or confirm the visible printed information. Any well knownoptical system such as lens 29 of FIG. 1a serves to focus images of thisdocument coding pattern upon a corresponding matrix 28 of photocells orphototransistors, which may be positioned generally in the focal planeof lens 29. A photosensitive pick-up cell is positioned in matrix 28 forthe image of each possible spot position of the pattern on document 26.When a small cell area on document 26 has phos phorescent materialapplied to form a spot 27, and irradiation has developed a detectableoutput radiation from spot 27, then lens 29 focuses this radiation uponthe particular cell of matrix 28 which corresponds to that spot 27 ondocument 26. The signals generated by cells activated in this manner arefed by leads 30 of cable 31 to amplifier 32, which serves to producecorresponding output signals at the leads 33.

Because they are invisible without processing and do not interfere withvisible printed data on document 26, spots 27 can be of comparativelylarge area and therefore positioning of document 26 is not critical. Asan alternative to large-area spots, amplifier 32 can be constructed tobe responsive to particular signals generated by the scanning ofparticular patterns of spots 27 and of spaces on the document having nophosphorescent material. In this further case, the matrix 28 shouldextend to a greater number of positions along each co-ordinate thandocument 26 requires, so positioning still would not be critical, eventhough the relative positioning of cells in matrix 28 and of spots ondocument 26 could be a precise, fine-detailed pattern. This can bevisualized by regarding the pattern of spots 27 shown on document 26 inFIG. lc. A separate photocell of matrix 28 will be energized for eachspot 27 shown. Then, when the sampling switch of amplifier 32 contactslead 30 in sequence, a particular sequence of signal and no-signalintervals will be generated, which is characteristic of the pattern ofspots 27 on document 26. Equipment can be made responsive to particularsequences, just as Teletype equipment responds to Teletype signalsequences, and not be sensitive to which of leads 30 are used to producethis sequence. In other words, the number of photocells in matrix 28exceeds the number of coding areas on document 26, so document 26 has awide tolerance on its position beneath lens 29 in which scanning willproduce the desired sequence even though varying the position ofdocument 26 will vary the actual separate photocells transmitting thesequence via lines 30. Thus the sequence and hence the digital signal onleads 33 would not be destroyed by mispositioning of the document.

In addition to the desired luminescent material in spots 27, otherunwanted luminescent areas 42 also are present. Areas 42 on the documentare used to designate areas containing unwanted fluorescent materialssuch 'as dirt, grease, smudges, chemical residues, etc. Usually, theyare of short-persistence fluorescence, as contrasted to spots 27 whichare of long-persistence phosphorescence. As shown in FIG. 1b, outputsignals are obtained from amplifier 32 at leads 33. The actual form ofsignals used is not pertinent to this invention. For example, outputsignals may be digital in nature, with the digital timing "determined bysampling switch of amplifier 32, and the 'on or off signal statusdetermined by energization of photocells in matrix 28 applying voltageto particular ones of leads 30. This sampling switch must scan all leads30 during each duty cycle as fixed by energization of leads 23. Theseduty cycles are time-shared with duty cycles for radiation sources 24and 25. This time-sharing mode of operation presents marked improvementsin the reading of normally invisible, luminescent markings. With radiantenergy sources 24 and 25 and amplifier 32 connected for continuousrather than time-sharing operation, severe noise levels or maskingbackground signal would be encountered, under some conditions. Analysisshows three main noises to be present: (a) scattered or diffusereflection of the incident radiation back to photosensitive matrix 28;(b) radiation from unwanted fluorescence of bleaches, smudges and otherforeign materials in areas 42 on the document; and (0) electrical fieldnoise generated in the activation of radiation sources, and picked up inthe matrix 28 or its wiring 30. When the source of irradiation is turnedoff, all of these noises subside very rapidly, much more rapidly thendoes the radiation from the phosphorescent spots 27 which are of longpersistence. Accordingly, spots 27 continue to energize cells of matrix28 after background noise subsides, providing a marked improvement insignal-to-noise ratio over prior art reading techniques. Preferably alighttight enclos'ureshown here, for illustrative purposes, with thefront wall removedis provided by walls 34 surrounding thedocument-scanning position and connected to the structure of sources 24and 25 to reduce any reflection, excitation or difiusion from externallyincident radiant energy.

FIG. 2 illustrates the time relationships of the novel mode of operationsuggested by the present invention. Radiation sources 24 and 25 are onfor the pulse period 43 from zero (0) to T during which all fluorescentmaterials 42 rise to a radiation output amplitude related to theincident radiation, as shown by the leading edge 44 of waveform 40.During this same interval, 0 to T all phosphorescent materials of spots27 also rise to a maximum radiation output related to incident radiationas shown by the leading edge 46 of waveform 41. For convenience, theseare indicated as a common level Im reached under sustained irradiationat time T The radiation sources 24 and 25 are cut off at time T and thephotosensitive pickup system of photocell matrix 28 and amplifier 32 isenergized at time T During this interval T -T the unwanted fluorescenceof dirt, chemical residues, dirt, etc., shown on the document as spots42 will decay rapidly. The trailing edge 45 of curve 40 shows a typicalradiation decay curve for such fluorescent materials as spots 42.Contrasted to curve 40, the decay time for phosphorescent materials incoded spots 27 is considerably longer, as shown by the trailing edge 47of curve 41. Beginning at time T and for a period T T the photocellmatrix 28 responds to radiation from spots 27 and amplifier 32 respondsto the signals from matrix 28. Since a delay time has been providedduring which radiation from unwanted fluorescence has subsided, therewill be little or no signal from areas 42. From an examination of curves40 and 41 it can be seen that the ratio of signal (curve 41) to noise(curve 40) during this period T T is increased considerably over that insystems employing continuous irradiation. To this is added the increasein ratio of wanted signal to unwanted radiation and noise, arising fromremoval of incident irradiation andelectrical noise which also effectthe signal-to-noise ratio adversely.

In lieu of an electrical output signal at leads 33, the photosensitivepickup matrix 28 can be replaced by a recording camera 35, as shown inFIG. 3. Camera 35 is mounted with an electrically actuated shutter 36functioning to open for passage of radiation when a voltage is appliedto leads 23. Radiation sources 24 and 25 function as described before.When X-rays are used, appropriate shielding must be included in housing34 and around the camera 35. The time relationship between voltagesapplied to leads 22 and 23 is shown by waveforms 37 and 38. Theradiation sources 24 and 25 irradiate document 26 during a pulse of wave37. After this irradiation, shutter 36 is opened and the film 39 incamera 35 is exposed to the phosphorescent radiation from spots 27. Thecontrast characteristic of film 39 can be selected to provide maximumdiscrimination against the lower level light from the unwantedfluorescent materials, shown as curve 40 in FIG. 2, and maximum emphasisof the higher level light from the phosphorescent materials of spots 27,shown as curve 41 in FIG. 2. It is evident that with film 39 anddocument 26 statically positioned, the waveforms 37 and 38 will actuateradiation sources 24 and 25 and shutter 36 to produce multiple exposureswhich emphasize the long-persistence phosphorescent radiation from spots27 However film 39 can be fed automatically by mechanisms such as thatin the commercially available Robot camera and documents also can be fedin an automatic manner. Both automatic feeds can be triggered or drivenby Waveforms 37 and 38, through solenoids or quick starting electricmotors, in ways well known to those skilled in the art. Such automaticfeed of film and documents would be useful to record a number ofdocuments when a single high-intensity irradiation of a document andsubsequent exposure of the film produces adequate density of theresulting photograph. Further, a manual switch could be used to switch avoltage source from a normal position on line 22 to a scanning positionon line 23. As this switch is actuated, radiation sources 24 and 25 arecut off, fluorescence of areas 42 subsides, leaving phosphorescence ofspots 27, and shutter 36 is opened to record the radiation from spots27.

As shown in FIGS. 4a and 4b, and in accordance with the form of thepresent invention claimed in the parent application identified above,the time delay between irradiation and scanning, necessary to permitunwanted fluorescence to subside before desired phosphorescence isscanned, is provided by an optical system. FIG. 4a is a front elevationview of a housing 34, with its front wall removed, for a rotating mirrorassembly 50, with document 26, radiation source 57, and photoelectriccell 58 facing the mirror assembly as shown. With reference to FIG. 4bit will be seen that source 57 and cell 58 are immediately belowdocument 26 and that rotating mirror assembly is driven by motor 6%).Mirror assembly 50 comprises five plane mirrors 51 to mounted around theaxis of rotation to form a pentagon. It is evident that either greateror lesser numbers of mirrors could be so mounted, forming a triangle,square, hexagon, etc. Each plane mirror 51 to 55 is tilted at an anglerelative to the axis of rotation of mirror assembly 50 which isdifferent from the tilt angle for other mirrors, so that each mirrorreflects a ray from source 57 to a difierent area of document 26, aswill now be described.

Radiation source 57 includes a collimator to align its outgoingradiation into ray 56. Ray 56 strikes whichever mirror of mirrors 51 to55 is positioned to reflect it. As shown in FIG. 4a, mirror 52 is insuch a position and reflects ray 56 back to document 26. Photocell 58also includes a collimator aligned with ray path 59. In effect,photocell 58 can see only the small area of document 26 aligned with ray59. With mirror assembly 50 rotating counterclockwise as shown in FIG.4a, the portions of rays 56 and 59 from mirrors to document 26, willsweep across the document from left to right. If the planes of allmirrors 51 to 55 were mounted at the same angle relative to the axis ofrotation, then the successive sweeps of rays 56 and 59 across document26- would be, on the same path across the document for reflection fromeach mirror. However, each mirror has its plane at a different anglerelative to the axis of rotation. These differing angles of tilt areshown as dotted lines 64 and 65 in FIG. 4b. Only two such angles of tiltare shown to simplify the drawing. Line 64 of less tilt than line 65 isthe plane of mirror 54 of minimum tilt angle, while :line 65 would befor mirror 55 of maximum tilt angle.

As shown in FIG. 40, mirror 54 has minimum or zero tilt, mirror 53 hasnext larger tilt angle, mirror 52 has next larger tilt angle, and so onuntil the last successive mirror, mirror 55 of the pentagon, is reached.Then the first mirror 54 again comes around to return the rays to thepath for minimum tilt angle. As shown in FIG. 412, this axial tiltcauses the rays 56a, b and c together with their corresponding rays 59,for radiant energy and for the viewing ray of the photocellrespectively, to sweep document 26 along a different line for eachmirror. Line 56a is the ray path from mirror 54 to document 26, line 56bis the ray path from mirror 52 to document 26, and line 560 is the raypath from mirror 55 to document 26. Accordingly, it is evident that, inaddition to the sweep of rays 56 and 59 across the document from left toright as seen in FIG. 4a, there is a displacement of each sweep to aseparate path as shown in FIG. 4b, as motor rotates the mirror assembly50. Because of the spaced relation of rays 56 and 59 and the directionof rotation of mirror 50, ray 59 or the viewing ray of photocell 58sweeps over any given area of document 26 shortly after that spot isirradiated by ray 56. The speed of rotation of mirror 50 can be utilizedto adjust the time interval between irradiation and scanning. Motor 60is preferably provided with a variable speed drive for this purpose.However, in determining a speed of rotation needed for a given sweepspeed of rays 56 and 59 across document 26, it must be remembered thatthe angular velocity 'of the rays sweeping across document 26 is twicethe angular velocity of mirror system 50. This relation exists becausethe angle of incidence equals the angle of reflection and the source anddocument are both stationary. Consider movement of the mirror through,say, degrees rotation. This changes the angle of incidence of a ray thesame 5 degrees. This in turn changes the rays angle of reflectionanother 5 degrees, so that the angle between incident and reflected rayshas changed degrees.

With this optical method of introducing a time delay between irradiationand scanning so that fluorescence can subside, it is unnecessary to"gate with electrical signals the source 57 or detector device 58. Theoutput signal from detector device 58 will be dependent uponspotscanning speeds, spot distribution on the document, and persistencetime for spots 27 The first two parameters generate the signalsconveying the information stored in the spots, and the last parameteraffects the ratio of this signal to background noise, the noiseincluding radiation from unwanted fluorescence. As shown in FIGS. 4a and4b, with a multi-sided mirror and with each mirror tilted to scan adifferent line or zone of the document, a large matrix of digitallycoded information can be scanned in a very short interval to developserially presented electrical signals at the photocell 58. The number ofseparate lines from which coded data may be read, as seen in FIG. 4b, isdetermined by the number of differently tilted plane mirrors in mirrorsystem 50. Each tilt angle places the ray paths on a different line. Theoutput signals of detector device 58 will be digital in nature, due tothe scanning sequence of the ray paths generated by rotating mirrorsystem 50.

Time sharing between irradiation and scanning may be providedmechanically in the embodiment shown in FIGS. 5 and 6, and in accordancewith the form of the invention claimed in the present application. Disc61 is rotated, presenting aperture 62 first to radiation source 57 andthen to the photosensitive pickup device 58 which are the same generaltypes as those used in FIGS. 4a and 4b. For more adequate scanning, aplurality of apertures can be provided and the source and pickuppositioned to insure that irradiation is cut oflf before the pickup cellis exposed to luminescent sources of radiation. In this interval betweenirradiation and exposure of the cell, unwanted fluorescence subsides andthen the desired phosphorescence from spot 27 activates thephotosensitive pickup more reliably due to the reduced background noise,providing an enhanced signal to noise ratio. Scanning is provided eitherthrough motion of document 26 or by conventional Nipkow disc techniques,with rotation of disc 61 providing very frequent looks at document 26 sono spots 27 or untreated areas for such a spot are missed as eitherdocument 26 or the disc aperture pattern is moved. Since the exposure ofphotocell 58 is in short, frequently repeated intervals, it provides abasic signal frequency when radiation is received, so a digital signalis provided on an alternating carrier voltage, the frequency of which isdetermined by the frequency of passage of aperture 62.

From an examination of these embodiments of this invention it is seenthat the reading of data which has been deposited in luminescentmaterial upon a document is markedly improved in reliability and in thereduction of errors or spurious signals through the use oflongpersistence material for such data and in reading the radiation fromthis material after it is no longer exposed to irradiation andshort-persistence luminescence from unwanted luminescence sources hassubsided. As in most communication systems of limited intrinsicresolving power, increase in the signal-to-noise ratio can be dependedupon to improve reliability of the systems performance.

What is claimed is:

Apparatus for reading a document upon which data is coded in a patterncomprising a plurality of successive discrete areas of long persistenceluminescent materials and upon which short persistence luminescentmaterials may be deposited incident to processing and handling saiddocument, a housing, a lens in said housing, said housing having an areaon one side of said lens but spaced therefrom and through which saiddocument moves in passing through said housing, means in said housingproviding a source of radiant energy capable of and positioned tosuccessively irradiate the coded pattern of materials on said documentas it passes through said housing, utilization means positioned on theother side of said lens successively to receive the radiant energyresulting from the successive irradiation of said discrete areas of thecoded pattern of materials on said document, and control means forproviding a predetermined time interval between irradiation of saidmaterials and the radiation reception by the utilization means in orderto enable said utilization means to respond to radiation from said longpersistence luminescent materials on the document only after radiationof said short persistence materials has subsided, said control meanscomprising an opaque rotatable member interposed in the ray pathsbetween said source and said document and between said utilization meansand said document and having an aperture therein so that in one positionof its movement it cuts off one of said ray paths while permitting theother ray path to be opened and in another position of its movement itopens the formerly closed ray path while cutting off the formerly openray path, the movement of said member between the two positions and itsfunction in concurrently opening one and cutting off the other of thetwo ray paths serving to provide a predetermined time delay betweenirradiation of said materials on the document and the reception thereofby the utilization means whereby said utilization means is effective toproduce an output record only of the coded pattern of long persistenceluminescent materials on said document.

References Cited in the file of this patent UNITED STATES PATENTS2,240,844 Goggen et al May 6, 1941 2,334,475 Claudet Nov. 16, 19432,704,634 Rauch Mar. 22, .1955 2,742,631 Rajchman et a1 Apr. 17, 19562,794,945 Celmer June 4, 1957

